Knowledge Bank

The molecule sym-triazine $(C3H3N3)$ is the most symmetric azabenzene. We have measured the one-photon vibronic transition $60S1S1$ at 317 nm by laser induced fluorescence. The combination of a cw intracavity doubled ring dye laser with a molecular beam allowed the observation of completely resolved rotational lines. A complete rotational assignment could be given up to $J-5$. Like in other azabenzenes, the high resolution spectrum is perturbed by a mixing of singlet and triplet states. The nature of these states is confirmed by a strong dependence of the spectrum on an applied magnetic field. The number of lines clearly proves that sym-triazine is in the small-molecule limit. The linewidth is not constant, but varies between 12 MHz (the instrumental width) for the strong lines to 50 MHz for the weak lines. This indicates that there is a strong state dependent internal conversion in sym-triazine